1. Field of the Invention
The present invention relates to a liquid jet recording head for ejecting a recording liquid in the form of droplets through minute ejection orifices, thereby recording an image on a recording medium, and a method of manufacturing the liquid jet recording head.
2. Description of the Related Art
A liquid jet recording apparatus is one of the so-called non-impact type recording apparatuses, and has the features that it is capable of recording an image on various types of recording media at a high speed, and hardly generates noise during the recording. Because of those features, the liquid jet recording apparatus has been widely employed as a recording mechanism in printers, word processors, facsimiles, copying machines, etc.
As a typical example of liquid jet recording techniques for use in that type of liquid jet recording apparatus, there is known one using an electrothermal transducer as an ejection energy generating element. According to this technique, droplets of a recording liquid are ejected through minute ejection orifices to record an image on a recording medium. A liquid jet recording apparatus employing such a technique comprises, generally, a recording head including ejection nozzles to form droplets, and a recording liquid supply system for supplying a recording liquid to the recording head. A liquid jet recording head using electrothermal transducers is constructed such that the electrothermal transducers are arranged in a pressurized chamber, an electrical pulse representing a recording signal is applied to each of the electrothermal transducers for giving thermal energy to a recording liquid, and droplets of the recording liquid are ejected by utilizing bubble pressure resulting from bubbling (boiling) of the recording liquid, which is produced as a result of a phase change of the recording liquid caused upon application of the thermal energy.
Furthermore, the liquid jet recording head using electrothermal transducers is divided into two types, i.e., one (edge shooter type) wherein the recording liquid is ejected parallel to the board on which the electrothermal transducers are arranged, and the other (side shooter type) wherein the recording liquid is ejected perpendicular to the board on which the electrothermal transducers are arranged.
FIG. 11 (consisting actually of FIGS. 11A, 11B and 11C) shows a conventional typical board (referred to as a xe2x80x9crecording element substratexe2x80x9d hereinafter) on which electrothermal transducers are arranged and which has the function of ejecting a recording liquid. Specifically, FIG. 11A is a plan view, FIG. 11B is a bottom view, and FIG. 11C is a side view. FIG. 12 shows the recording element substrate of FIG. 11 connected to a wiring board.
As shown in FIGS. 11A to 11C, a recording element substrate 101 has a through hole (recording liquid supply port) 103 formed therein for supply of a recording liquid from the rear surface side of the board 101. A plurality of electrothermal transducers (not shown) for applying ejection energy to the recording liquid are arranged on the surface of a substrate 102 on both sides of the through hole 103. Further, an ejection plate 105 is disposed on the substrate 102, and a plurality of ejection orifices 106 are formed in the ejection plate 105 opposite to the plurality of electrothermal transducers in a one-to-one relation. A plurality of electrodes 107 are provided on the surface of the substrate 102 at both ends thereof for electrical connection to the plurality of electrothermal transducers.
Also, as shown in FIG. 12, a recording element unit 120 is constructed such that the plurality of electrodes 107 provided on the recording element substrate 101 and a plurality of electrode leads 113 provided on a flexible film member 111 are electrically connected to each other by the TAB technique, for example. These electrical connection areas are each entirely coated by a sealing resin 119 for protection against corrosion caused by the recording liquid and breakage of wires due to externally acting forces.
FIG. 13 is an external appearance perspective view showing one structural example of a conventional liquid jet recording head in which the recording element unit of FIG. 12 is incorporated.
European Patent Application Laid-Open Publication No. EP0822078A2 shows a liquid jet recording head which is one example of the conventional liquid jet recording head, shown in FIG. 13, in which the recording element unit of FIG. 12 is incorporated. FIG. 14 is a partial enlarged sectional view, taken along line Axe2x80x94A in FIG. 13, of the liquid jet recording head of that Publication.
In the liquid jet recording head disclosed in that Publication, as shown in FIGS. 13 and 14, the recording element unit is fixedly bonded to an upper surface of a support member 108 by a bonding resin A 121. Further, a support plate 109 is fixedly bonded to the upper surface of the support member 108 by a bonding resin B 122, and the flexible film member 111 is fixedly bonded to an upper surface of the support plate 109 by a bonding resin C 123. Also, a second wiring board 116 is held on and fixed to a lateral surface of the support member 108, and an external input pad 115 for applying an electrical signal, such as recording information, to the liquid jet recording head from the body side of a recording apparatus is provided on the second wiring board 116. The second wiring board 116 is electrically connected to a plurality of recording element units through flexible film members 111a, 111b, 111c and 111d. 
Thus, in the liquid jet recording head of European Patent Application Laid-Open Publication No. EP0822078A2, the recording element substrate and the wiring board are electrically connected to each other by leads, and a second sealing resin is applied to an electrical connection area between both the boards. Then, the recording element substrate is fixedly joined to the support member, the wiring board is fixedly bonded to the support plate, and a first sealing resin is filled into a recess formed between the support plate and the recording element substrate. Stated otherwise, since the first sealing resin is filled into the recess formed between the support plate and the recording element substrate in a state where the second sealing resin has been applied to the electrical connection area between the recording element substrate and the wiring board, a hollow space often occurs below the electrical connection area. In such a case, the recording liquid may enter the hollow space and corrode wires formed on the flexible film member 111.
In view of the above problem, U.S. patent application Ser. No. 09/488,931 proposes a method of employing a thermosetting material as the first sealing resin, and very reliably filling the first sealing resin, under heating, into a space below the electrical connection area to which the second sealing resin has been applied. This invention utilizes the property of the thermosetting material that it has a higher fluidity in an initial state of the heating and is then hardened.
Also, in a liquid jet recording head disclosed in that U.S. patent application, materials having substantially the same components are used as the first sealing resin filled into the space around the recording element substrate 101 and the second sealing resin sealing the electrical connection area between the recording element substrate 101 and the wiring board 111. The first sealing resin and the second sealing resin are heated and hardened in the same step. Because the material selected for sealing the electrical connection area between the recording element substrate 101 and the wiring board 111 is required to become very hard after hardening, for protection against external forces, a material containing an epoxy resin as a main ingredient is used for both the first and second sealing resins.
However, the recording element substrate 101 is vulnerable to external forces acting perpendicularly to the longitudinal direction (length) of the recording liquid supply port 103, from the structural point of view. Accordingly, if the sealing resin having the above-mentioned properties is filled in the recess formed beside the recording element substrate 101 on the side opposite to where the electrical connection is formed between the recording element substrate 101 and the wiring board 111, there occurs a risk that the recording element substrate 101 may be cracked and damaged by forces imposed during shrinkage of the sealing resin during hardening. Therefore, the sealing resin can be filled in sufficient amount into one of the recesses formed around the recording element substrate 101 which is positioned on the side locating below the electrical connection area between the recording element substrate 101 and the wiring board 111 (i.e., on the side perpendicular to the longitudinal direction of the recording liquid supply port 103). As shown in FIG. 15, however, into a recess 117 formed laterally of the recording element substrate 101 on the side parallel to the longitudinal direction of the recording liquid supply port 103, the sealing resin can be applied just to such an extent that the sealing resin coats the lateral surfaces of the recording element substrate 101 and the support plate 109 for protection against corrosion due to the recording liquid and short-circuiting through the recording liquid. In other words, a sufficient amount of sealing resin cannot be filled in the recess 117, unlike the liquid jet recording head shown in the above-cited EP Publication. When the amount of sealing resin filled in the recess 117 is insufficient, there may occur the following problem. The recording liquid scattered during printing or wiping of the head for cleaning, is gradually accumulated in the recesses formed on both sides of the recording element substrate, and remains there, with increased viscosity. Then, the recording liquid having the increased viscosity adheres to a wiper during the wiping of the head. Further, if the recording liquid having the increased viscosity adheres to the ejection orifices, a trouble may occur in the process for stably ejecting droplets of the recording liquid.
Moreover, in the conventional liquid jet recording heads described above, the flexible film member has a narrower width than the support plate and is bonded to the upper surface of the support plate inward of its outer periphery. Therefore, if a bonding resin for joining the flexible film member and the support plate to each other spreads out of the flexible film member when applied, the spread-out bonding resin adheres to a heater used for joining the flexible film member to the support plate by heat-pressing and then hardens. In such an event, production of defective heads continues until hardening of the bonding resin on the heater is discovered. Then, the production line must remain stopped until the replacement of the existing heater and the adjustment of a new heater are completed.
The present invention has been accomplished with the view of overcoming the above-mentioned problems in the related art, taking into account that materials of sealing resins should have different suitable properties depending on areas to be sealed by the sealing resins. It is an object of the present invention to provide a liquid jet recording head and a method of manufacturing the head, in which a sufficient amount of sealing resin can be filled into a space below an electrical connection area between a recording element substrate and a flexible film member; the recording element substrate is not damaged upon a shrinkage of the sealing resin during hardening even when the sealing resin is applied in an amount sufficient to fully fill recesses formed around the recording element substrate; and the electrical connection area between the recording element substrate and the flexible film member can be protected against external forces that occur upon, e.g., wiping of the head.
Another object of the present invention is to provide a liquid jet recording head and a method of manufacturing the head, with which efficient production can be realized by simultaneously carrying out steps of hardening (curing) a plurality of sealing resins made of different materials.
Still another object of the present invention is to provide a liquid jet recording head and a method of manufacturing the head, which can prevent deterioration of printing quality caused when a sealing resin for protecting an outer periphery of the flexible film member against the recording liquid is brought into contact with a recording medium.
Still another object of the present invention is to provide a liquid jet recording head and a method of manufacturing the head, which can eliminate the causes of inviting failures in the bonding step and can realize stable production.
To achieve the above objects, the present invention provides a liquid jet recording head comprising at least one recording element unit comprising a recording element substrate including a plurality of recording elements for ejecting a recording liquid, and a flexible film member having an opening in which the recording element substrate is assembled, and electrically connected to the recording element substrate for applying electrical energy to the recording element substrate for ejection of the recording liquid, the flexible film member including a plurality of electrode leads which are provided along edges of the opening of the flexible film member and are electrically connected to a plurality of electrode pads provided along edges of the recording element substrate; a support member on which the recording element substrate is fixedly held; and a support plate having an opening into which the recording element substrate is inserted, situated between the flexible film member of the recording element unit and the support member, and fixedly holding the flexible film member. A first thermosetting resin agent having elasticity even after being hardened is filled into recesses formed around the recording element substrate within the opening of the flexible film member and the opening of the support plate, and electrical connection areas between the recording element substrate and the flexible film member are coated by a second thermosetting resin agent, which has a higher mechanical strength after being hardened than that of the first resin agent.
With the thus-constructed liquid jet recording head of the present invention, since the first sealing resin fills in the recesses which are formed around the recording element substrate within the opening of the flexible film member and the opening of the support plate, and has elasticity even after being hardened, there is no risk that the recording element substrate may suffer from cracks or other damages upon a shrinkage of the first resin agent during the hardening. Further, since the electrical connection areas between the recording element substrate and the flexible film member are coated by the second resin agent having a higher mechanical strength after being hardened than that of the first resin agent, those electrical connection areas can be protected against external forces that occur during, e.g., wiping of the head.
The first resin agent may be a thermosetting silicone-modified epoxy resin, and the second resin agent may be a thermosetting epoxy resin.
An outer periphery of the flexible film member may be sealed by a sealing agent. This feature is effective to prevent corrosion of the outer periphery of the flexible film member due to the recording liquid.
Preferably, the flexible film member is formed so as to completely cover an upper surface of the support plate and to extend out of an outer peripheral edge of the support plate. With this feature, the sealing resin can be applied to a rear surface (side facing the support member) of a portion of the flexible film member, which is extended out of the outer peripheral edge of the support plate. It is therefore possible to not only prevent the resin agent from adhering to a heater for joining the flexible film member to the support plate by thermal pressing, but also prevent the resin agent from spreading out to the surface side of the flexible film member and deteriorating printing quality due to contact of the spread-out resin agent with a recording medium.
In that case, more preferably, the sealing agent is applied along a surface of the portion of the flexible film member, which is extended out of the outer peripheral edge of the support plate, the surface facing the support member, and along an outer peripheral surface of the support plate.
When the first resin agent and the sealing agent are made of the same material, the first resin agent and the sealing agent can be applied in the same step and hardened at the same time.
The first resin agent and the sealing agent may be made of a thermosetting silicone-modified epoxy resin.
Also, the present invention provides a method of manufacturing a liquid jet recording head comprising at least one recording element unit comprising a recording element substrate including a plurality of recording elements for ejecting a recording liquid, and a flexible film member having an opening in which the recording element substrate is assembled, and electrically connected to the recording element substrate for applying electrical energy to the recording element substrate for ejection of the recording liquid, the flexible film member including a plurality of electrode leads which are provided along edges of the opening of the flexible film member and are electrically connected to a plurality of electrode pads provided along edges of the recording element substrate; a support member on which the recording element substrate is fixedly held; and a support plate having an opening into which the recording element substrate is inserted, situated between the flexible film member of the recording element unit and the support member, and fixedly holding the flexible film member. A first thermosetting resin agent having elasticity even after being hardened is filled into recesses formed around the recording element substrate within the opening of the flexible film member and the opening of the support plate, and electrical connection areas between the recording element substrate and the flexible film member are coated by a second thermosetting resin agent, which has a higher mechanical strength after being hardened than that of the first resin agent. The method comprises joining the support plate to a predetermined position on the support member; joining the recording element substrate of the recording element unit to a predetermined position on the support member through the opening of the support plate, and joining the flexible film member onto the support plate; electrically connecting the plurality of electrode leads of the flexible film member respectively to the plurality of electrode pads of the recording element substrate; filling the first resin agent into the recesses; coating the electrical connection areas by the second thermosetting resin agent which has a higher mechanical strength after being hardened than that of the first resin agent; and heating the first resin agent and the second resin agent after the step of filling the first resin agent into the recesses and the step of coating the electrical connection areas by the second resin agent.
With the method of manufacturing a liquid jet recording head according to the present invention, it is possible to manufacture a recording head which is free from a risk that the recording element substrate may suffer from cracks or other damages upon a shrinkage of the first resin agent during the hardening, and in which the electrical connection areas between the recording element substrate and the flexible film member can be protected against external forces that occur during, e.g., wiping of the head.
Further, since the first resin agent and the second resin agent can be hardened at the same time under heating, production efficiency can be improved in comparison with the case of carrying out the steps of curing the first resin agent and the second resin agent successively.
The first resin agent may be filled into the recesses after the step of coating the electrical connection areas by the second resin agent. With this feature, even when the first resin agent is poured from both outer peripheral sides of the recording element substrate parallel to a recording liquid supply port, air residing below the electrode leads can escape through gaps between the electrode leads, thereby enabling the first resin agent to flow to all corners of the recesses. As a result, the first resin agent can be applied so as to fill the overall recesses without leaving hollow spaces below the electrode leads.
Conversely, the electrical connection areas may be coated by the second resin agent after the step of filling the first resin agent into the recesses. In this case, by pouring the first resin agent from one outer peripheral side of the recording element substrate parallel to the recording liquid supply port, the first resin agent is caused to flow to all corners of the recesses, whereby the first resin agent can be applied so as to fill the overall recesses without leaving hollow spaces below the electrode leads.
The step of electrically connecting the plurality of electrode leads of the flexible film member respectively to the plurality of electrode pads of the recording element substrate may be performed by gang bonding for connecting all of connection points at a time.
Alternatively, the step of electrically connecting the plurality of electrode leads of the flexible film member respectively to the plurality of electrode pads of the recording element substrate may be performed by single-point bonding for connecting connection points one by one successively.
Alternatively, the step of electrically connecting the plurality of electrode leads of the flexible film member respectively to the plurality of electrode pads of the recording element substrate may be performed by wire bonding for connecting connection points one by one successively.
Alternatively, the step of electrically connecting the plurality of electrode leads of the flexible film member respectively to the plurality of electrode pads of the recording element substrate may be performed by an ACF connecting method.
When the flexible film member in the liquid jet recording head is formed so as to completely cover an upper surface of the support plate and to extend beyond an outer peripheral edge of the support plate and an outer periphery of the flexible film member is sealed by a sealing agent, the method of manufacturing the liquid jet recording head may comprise: joining the support plate to a predetermined position on the support member; joining the recording element substrate of the recording element unit to a predetermined position on the support member through the opening of the support plate, and joining the flexible film member onto the support plate such that the flexible film member completely covers the upper surface of the support plate and its outer peripheral edge extends beyond the outer peripheral edge of the support plate; electrically connecting the plurality of electrode leads of the flexible film member respectively to the plurality of electrode pads of the recording element substrate; and applying the sealing agent to the outer periphery of the flexible film member.
With the above method of manufacturing a liquid jet recording head according to the present invention, it is possible to manufacture a recording head which can not only prevent the resin agent from adhering to a heater for joining the flexible film member to the support plate by thermal pressing, but also prevent the resin agent from spreading out to the surface side of the flexible film member and deteriorating printing quality due to contact of the spread-out resin agent with a recording medium.
Preferably, the step of applying a sealing agent to an outer periphery of the flexible film member comprises the step of supplying the sealing agent to only one point of the outer periphery of the flexible film member so that the sealing agent flows to the entire outer periphery of the flexible film member due to capillary forces acting in a region surrounded by a surface of a portion of the flexible film member, which extends beyond the outer peripheral edge of the support plate, the surface facing the support member, an outer peripheral surface of the support plate, and a surface of the support member facing the flexible film member.
Also preferably, the method of manufacturing a liquid jet recording head further comprises: filling the first resin agent into the recesses formed around the recording element substrate within the opening of the flexible film member and the opening of the support plate; coating the electrical connection areas between the recording element substrate and the flexible film member by the second resin agent; and heating the sealing agent, the first resin agent and the second resin agent after the steps of filling, coating and applying.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.